Fuel injectors for internal combustion engines or fuel cells are well known. A typical fuel injector comprises a fuel metering valve disposed in a first end portion for insertion into an engine cylinder intake port; an electric solenoid actuator for actuating the valve; and a central fuel tube for receiving fuel from a fuel source such as a fuel rail and conveying the fuel axially through the solenoid to the metering valve. Disposed within the fuel tube is a calibration tube which acts as a seat for a valve-closing coil spring, the compression of which is determined by the axial position of the calibration tube within the fuel tube. In flowing through the fuel tube, fuel also flows through the calibration tube. Disposed within the calibration tube is a plastic filter comprising an integral screen filter medium having a nominal pore size of, typically, about 30 μm.
Prior art fuel filters are subject to at least two serious operational shortcomings because the filter medium is essentially a surface screen. First, the particulate-retention capacity is undesirably small; that is, the filter may be partially or even fully blocked by relatively little particulate matter, especially by large particles. Second, as the filter begins to plug, the pressure drop across the filter increases, which may force particles through the filter with consequent fouling of the metering valve, causing failure of the fuel injector.
Further, because flow through the filter is essentially radial, an annular fuel flow space must be provided between the filter and the calibration tube, which increases the diameter of the fuel injector and thus increases the size and cost of the solenoid.
It is a principal object of the present invention to provide higher capacity fuel filtration for a fuel injector.
It is a further object of the present invention to increase the reliability of a fuel  injector.
It is a still further object of the invention to reduce overall dimensions of a fuel injector.